The present invention relates to an apparatus for adjusting the height of a seat for an automobile.
Referring first to FIG. 5, a typical conventional apparatus 1 for adjusting the height of a seat for an automobile basically has a handle 3 provided on a seat adjuster 2, a spring coupler 4 having a driving member operatively connected to the handle 3, a link 6 operatively connected to a driven member of the spring coupler 4 through a plate 5, and a rod 7 for connecting the link 6 mounted on one side of the seat and a link 6' on the other side. The reference numeral 8 denotes a bar for connecting together the link 6 and a link 6" disposed on the side of the apparatus 1 which is closer to the rear end of the vehicle. A seat frame is rigidly secured to the links 6, 6' and 6" using bores 9 respectively provided in these links.
Turning of the handle 3 in the direction of the arrow causes the link 6 to pivot in the same direction through the spring coupler 4, together with the other links 6' and 6", thus raising the seat. Since this seat raising operation is effected against the weights of the seat and an occupant seated therein, a relatively larger force is needed. The force required for actuating the handle 3 may be reduced by increasing the ratio of the distance between the center of pivotal motion of the handle 3 and the axis of the rod 6 to the length of the handle 3 and further employing a torsion spring 10 connected at one end thereof to the seat adjuster 2 and at the other end thereof to the link rod 7. The torsion spring 10 biases the link rod 7 in the direction in which the seat is raised.
Since the torsion spring 10 has a relatively high spring constant, the torque which acts about the link rod 7 shows a large gradient between the upper and lower positions of the seat, which means that it is impossible for this torsion spring 10 to be constantly balanced within a seat height adjustable range balance with the weights of the seat and an occupant seated.